Detection of histamine and histamine-related bacteria in fish-nukazuke, a salted and fermented fish with rice-bran, by simple colorimetric microplate assay

Effect of Fishing Season and Size on the Physicochemical and Microbiological Characteristics of Salted Sardines (Sardina pilchardus)

Salting is the preferred method used by manufacturers to preserve the quality of fish. The aim of this study was to investigate the effect of size and fishing season on the physicochemical and microbiological characteristics of sardines. Two batches of sardines, caught, in winter and summer, were sorted according to size, salted, matured, and stored at 18°C. A control batch, consisting of sardines from the summer batch, was also prepared without subcutaneous fat. Various physicochemical and microbiological parameters were monitored during 12 weeks of maturation. The recorded values showed a decrease in pH, moisture content, and water activity (a measure of the water available for biological and chemical processes), while salt concentration increased. When comparing samples, the lowest values for histamine (94.3 and 48.3 mg/kg) and lipids (9.3 and 8.2%) were observed in the large and small sardines of the winter batch, respectively. In the summer batch, higher values were recorded for histamine (847.3 and 127.9 mg/kg) and lipids (14.5 and 8.6%) in the large and small sardines. Furthermore, the removal of fat in control of the summer batch resulted in lower histamine accumulation compared to the batch with fat. The microbiological parameters showed a decrease in the number of nonhalophile bacteria, while the number of halophile bacteria increased. This study showed a strong correlation between three important factors, fishing season, fish size, and histamine content, which can contribute to the successful salting of sardines and ensure the wholesomeness of the final product.

The Impact of Sea Urchin as an Ingredient on the Physicochemical, Microbiological, and Sensory Properties of Fish Sauce Fermentation

The consequences of using 25% whole or shelled sea urchin as an ingredient in anchovy sauce on its fermentation and development of its physicochemical properties after 20 days fermentation was studied. Two varieties of fish and sea urchin sauce were made with or without shell at 1:2:1 ratio (salt:fish:sea urchin) plus a control fish sauce at 1:3 ratio (salt:fish). All sauces were fermented at 40-50 °C for 20 days, where for the first 7 days the preparation remained in a static phase. During their fermentation, pH, salt concentration, aw, TVB-N, TMA, total nitrogen, formaldehyde nitrogen, amino nitrogen, and ammonium nitrogen, as well as aerobic mesophiles and lactic acid bacteria were monitored. The fermentation of the experimental sauces proved to follow an evolution rather similar to the control sauce. The whole and shelled sea urchins provided the necessary microbial and enzymatic load to trigger an adequate hydrolysis of the fish and the production of total nitrogen (16.0-17.6 g/L), formaldehyde nitrogen (15.1-16.0 g/L), and amino nitrogen (0.7-0.8 g/L) of the same order as the control sauce, despite the lower fish content. According to TMA (9.2-13.1 mg N/100 g), VBT (40.0-47.2 mg N/100 g) contents, and pH levels (5.41-5.46), no deviation of the fermentation process was observed under the experimental conditions (salt content, temperature, and agitation after the static phase). Quantitative descriptive analysis (QDA) sensory revealed that the use of sea urchin results in high quality products characterized by their aromas of crustaceans and mollusks. The present study investigates the potential use of shelled and even whole sea urchin as an ingredient for the preparation of high quality fish sauces.

Evolution of Free Amino Acids, Histamine and Volatile Compounds in the Italian Anchovies (Engraulis encrasicolus L.) Sauce at Different Ripening Times

In this study, the evolution of the safety, nutritional, and volatile profile of a traditional Italian anchovy sauce with protected designation of origin (PDO), called "colatura di alici di Cetara", is investigated after 12, 24, and 48 months of aging in wooden barrels. Some physicochemical parameters, free amino acids, volatile compounds, and histamine contents were evaluated during the aging of the samples. Glutamate, which together with aspartate is responsible for the umami taste, was the predominant free amino acid in the tested fish sauce, with a significant increase during the 48 months of maturation. The total amino acid content of the anchovy sauce increased from 24 to 48 months of aging. The histamine content decreased significantly from 12 to 48 months of ripening. This point is particularly interesting for the sauce safety and confirms the importance of the maturation time of at least 9 months reported in the disciplinary of production. A total of 44 volatile compounds were found in the anchovy sauce samples, of which the largest class was acids, mainly isovaleric acid. The results show that prolonged maturation improves the safety, nutritional, and volatile components of the seasoning "colatura di alici".

Technological roles of microorganisms in fish fermentation: a review

Fermentation is an important way to process and preserve fish. It not only gives the product a unique flavor and texture, but it also contributes to increased nutritional value and better functional properties. The production of fermented fish relies on naturally occurring enzymes (in the muscle or the intestinal tract) as well as microbial metabolic activity. This review focuses on the role of microorganisms on texture change, flavor formation, and biogenic amines accumulation in fermented fish. In addition, the production conditions and the major biochemical changes in fermented fish products are also introduced to help understand the factors influencing the quality of fermented fish. Moreover, prospects for further research of fermented fish are discussed.

A highly selective "turn-on" electroanalysis strategy with reduced copper metal-organic frameworks for sensing histamine and histidine

A highly selective and sensitive electroanalysis strategy has been developed for sensing histamine (HTA) and histidine (His) with "turn-on" signal outputs using copper nanocomposites (Cu NCs) of reduced copper metal-organic frameworks (Cu MOFs). It was discovered that the Cu NC-modified electrodes could display the sharp and stable oxidation peaks of solid-state CuCl electrochemistry at a low potential (about -0.10 V). More interestingly, once HTA or His was introduced, the peaking currents of the electrodes would increase due to the specific interaction between Cu²⁺ and imidazole groups of HTA or His. A highly selective electroanalysis method was thereby developed for the detection of both HTA and His in the concentration range of 0.010-100 μM. Besides, the application feasibility of the developed electroanalysis strategy was demonstrated for the evaluation of HTA and His separately in red wine and urine samples. Such an electroanalysis candidate for HTA and His holds great potential for wide applications in the fields of food analysis and clinical disease diagnosis.

Quality, functionality, and microbiology of fermented fish: a review

Fermentation is a traditional food preservation method and is widely used for improving food safety, shelf life, and organoleptic and nutritional attributes. Fermented fish are produced and consumed in different parts of the world and are an integral part of many food cultures. Furthermore, fermented fish are a source of interesting microbes and are an important industry in many countries. This review tries to update the types and manufacturing processes for fermented fish around the world. The emphasis is on this work related to fermented fish and their health benefits, as well as the contribution of microorganisms to their fermentation. A variety of different approaches have been used to determine and understand microbial composition and functionality. Moreover, some challenges and future research directions regarding fermented fish are also discussed in this review. Further research into fermented fish products is of crucial importance not only for the food industry but also for human health. However, extensive in vivo and toxicological studies are essential before the application of bioactive-rich fermented fish products for human health benefits.

Dynamics and diversity of microbial community succession during fermentation of Suan yu, a Chinese traditional fermented fish, determined by high throughput sequencing

The main goal of this study was to investigate the dynamics, diversity and succession of microbial community present during the preparation of Suan yu (fermented fish), with and without starter cultures by high-throughput sequencing of 16S rRNA and ITS1 genes. Firmicutes and Ascomycota were the predominant phyla of bacteria and fungi, respectively, in all samples. At the genus level, Lactobacillus, Macrococcus and Staphylococcus were the predominating bacteria throughout the fermentation process, regardless of the inclusion of starter cultures. Saccharomyces was the predominating fungal genus in the early-fermentation stage of samples that inoculated starter cultures (MS), while the final product was dominated by Candida and Wickerhamomyces. Compared with naturally-fermented samples (NS; no starter cultures), Lactococcus, Leuconostoc, Enterococcus, Vibrio, Fusicolla and Torulaspora were inhibited and Aureobasidium emerged in samples inoculated with starter cultures (P < .05). Unweighted pair-group and principal component analyses of bacterial and fungal compositions revealed that microbiota structures differed between NS and MS samples. Redundancy analysis indicated that water content and pH might be important factors influencing the dominant bacterial and fungal community. Results indicated that microbial community were dynamic during fermentation process and the inoculation of mixed starter culture inhibited the growth of many organisms associated with food spoilage and contributed to the improvement of the quality of Suan yu products.

Comparison of PCR-DGGE and PCR-SSCP analysis for bacterial flora of Japanese traditional fermented fish products, aji-narezushi and iwashi-nukazuke

BACKGROUND

The bacterial flora of two Japanese traditional fermented fish products, aji-narezushi (salted and long-fermented horse mackerel (Trachurus japonicas) with rice) and iwashi-nukazuke (salted and long-fermented sardine (Sardinops melanostica) with rice bran), was analysed using non-culture-based polymerase chain reaction (PCR) denaturing gradient gel electrophoresis (DGGE) and culture-based PCR single-strand conformation polymorphism (SSCP) methods.

RESULTS

Viable plate counts in aji-narezushi and iwashi-nukazuke were about 6.3-6.6 and 5.7-6.9 log colony-forming units g(-1) respectively. In the PCR-DGGE analysis, Lactobacillus acidipiscis was detected as the predominant bacterium in two of three aji-narezushi samples, while Lactobacillus versmoldensis was predominant in the third sample. By the PCR-SSCP method, Lb. acidipiscis and Lactobacillus plantarum were isolated as the predominant bacteria, while Lb. versmoldensis was not detected. The predominant bacterium in two of three iwashi-nukazuke samples was Tetragenococcus muriaticus, while Tetragenococcus halophilus was predominant in the third sample.

CONCLUSION

The results suggest that the detection of some predominant lactic acid bacteria species in fermented fish by cultivation methods is difficult.

Occurrence of biogenic amines and polyamines in spinach and changes during storage under refrigeration

Biogenic amines and polyamines were studied in 18 market samples of spinach. Histamine and spermidine were detected in relatively high amounts in all samples within the ranges of 9.5-69.7 and 15.6-53.0 mg/kg, respectively. Other biologically active amines were either detected at low levels or not found at all. Changes in amine content during storage at 6 degrees C were studied. The content of most of the amines remained constant during storage, with the exception of spermidine and histamine. Spermidine showed a clear decreasing trend, whereas histamine significantly increased in all trials, but decreased at the end of the storage in two of the trials. Trials showing a decrease in histamine content also showed the highest spermidine decrease and recorded the highest pH values. Microbial loads throughout storage were also followed, with Pseudomonadaceae and Enterobacteriaceae being the predominant bacterial groups. Trials with higher microbial loads in initial samples also showed the highest histamine content in these samples. Potential explanations for both the formation and the degradation of histamine during storage are discussed.